1. Field of the Invention
The present invention relates to a plane motor suitable for a stage apparatus used for moving or positioning a substrate, the substrate being in a precision machine, such as a semiconductor exposure apparatus, or the like. A stage apparatus using the plane motor of the invention is used, for example, as a reticle stage or a wafer stage for sequentially moving a reticle or a silicon wafer with respect to a projection exposure system when performing projection exposure of the pattern of the reticle onto the silicon wafer in a projection exposure apparatus for transferring the pattern of the reticle onto the silicon wafer, the silicon wafer serving as a substrate to be exposed, in a semiconductor manufacturing process.
2. Description of the Related Art
In the field of high-precision apparatuses, such as semiconductor manufacturing apparatuses, and the like, in order to perform very precise position control at a high speed without depending on mechanical accuracy, and to obtain a long life by preventing mechanical friction, stage apparatuses for performing XY two-dimensional position control by driving a movable member in a two-dimensional direction in a non-contact state are being developed. Plane motors according to a variable reluctance driving method or an electromagnetic-force driving method using a Lorentz's force are used as driving sources for such stage apparatuses.
FIG. 10 illustrates a conventional stage apparatus used in a projection exposure apparatus. In FIG. 10, a stage apparatus 55 sequentially moves a substrate (wafer) 64 at each exposure operation. Reference numeral 61 represents a stage surface plate. A movable slider 62 is driven on the stage surface plate 61 in a two-dimensional direction in a non-contact state. An illuminance sensor 63 provided on the upper surface of the movable slider 62 performs calibration measurement of illuminance of exposing light before exposure in order to correct the amount of exposure. A wafer-conveying robot 57 supplies the stage apparatus 55 with the wafer 64. The wafer 64 is obtained by coating a resist on the surface of a single-crystal silicon substrate, in order to be subjected to projection transfer of a reticle pattern depicted on a reticle substrate via a reduction exposure system. An X-interferometer mirror 65 is a target for measuring the position of the movable slider 62 of the stage apparatus 55 in the X direction using a laser interferometer. Reference numeral 65A represents X-interferometer measuring light. An X-interferometer base 65B holds and positions the X-interferometer mirror 65. A Y-interferometer mirror 66 is a target for measuring the position of the movable slider 62 in the Y direction. Reference numeral 66A represents Y-interferometer measuring light. A Y-interferometer base 66B holds and positions the Y-interferometer mirror 66. In this and all other figures, X, Y and Z represent the respective directions (i.e., axes).
At present, a variable-reluctance-driving-type linear pulse motor is mainly used as the plane motor used in the stage apparatus shown in FIG. 10. This plane pulse motor includes the stage surface plate 61 on which comb-shaped magnetic members are arranged with an equal interval, and the movable slider 62 in which a plurality of armature coils having comb-shaped portions having a different phase facing the comb-shaped magnetic members and a permanent magnet form a yoke. By changing reluctance by causing a current to flow in the armature coils, a thrust for driving the movable slider 62 is generated. By controlling a pulse current supplied to each of the armature coils, a stepping operation is performed.
Although the above-described plane motor can perform very precise positioning and has excellent thrust linearity, a large current must be supplied in order to obtain a large thrust, thereby causing a problem of heating of the armature coils. Accordingly, in order to mitigate thermal influence, a design of cooling using a refrigerant, or the like, is in progress. However, since a yoke having armature coils generates a strong thrust, it is bonded to the movable slider using resin or an organic compound. Accordingly, it is difficult to form a refrigerant channel for efficiently cooling the armature coils. FIG. 11 illustrates a conventional cooling structure. In FIG. 11, there are shown a cooling-refrigerant inlet 71, a cooling-refrigerant outlet 72, and a cooling-channel direction 73. According to such a cooling method, heating of a corner portion 74 cannot be suppressed.
A plane motor according to an electromagnetic-force driving method using a Lorentz's force includes the stage surface plate 61 in which a permanent magnet magnetized so as to arrange a plurality of pairs of an S pole and an N pole with an equal interval is disposed, and the movable slider 62 in which an air-core armature coil wound so as to face the permanent magnet is disposed. In the plane motor of this type, by causing a current to flow in the armature coil, a Lorentz's force according to the Fleming's left-hand rule is generated to drive the movable slider 62. In this case, also, a structure for efficiently cooling the armature coil has been desired.
As described above, in plane pulse motors for stage apparatuses, although design of cooling has been proceeding in order to suppress influence by heat, a cooling structure having better efficiency is being requested. Furthermore, since the current movable slider and stage surface plate are integrated, an integrated structure must be newly manufactured when there is a change in specifications, such as an increase in the thrust, or the like.